KAREN BOOKER shed half her body weight only to pile most of it back on. Now, after losing it all again, she tells us why she’s determined to stay slim for life.

Standing on the scales and realising I'd lost 11st was an incredible moment, I couldn't believe I'd come so far. Yet I also had a sense of deja vu. It may seem hard to believe but I'd actually been in this position before.

Just three years earlier I had celebrated losing 12st. I'd followed my own diet and exercise plan and managed to lose a stone a month for a year.

But I couldn't keep it off. Once my motivation flagged, the pounds crept back on and within a year I'd piled on more than 7st. I was devastated. I knew I needed to find a way to slim down and stay that way for good.

I first started putting on weight as a child. My family struggled with their weight and I was no different, mainly because when it came to food I had no "off" switch.

I found eating a comfort from a young age. When I was well behaved I was rewarded with food such as sweets and chocolate.

School was really tough. While I did have a group of friends who stood by me, other classmates would bully me. The more unhappy I became the more food I ate and by the time I left school aged 16 I weighed more than 18st.

My weight continued to creep up. Whether sitting behind a desk where I worked for the council or lying on the sofa at home, my days revolved around food. I ate chips every day at work and takeaways with my husband Greg. By the age of 33 I had ballooned to 32st and was a massive size 38.

The older I got the more I felt like giving up on life completely. I was exhausted and embarrassed.

Shopping on the high street was out of the question and I had to buy my clothes from specialist online boutiques.

I tried lots of different diets but nothing worked until I managed to lose 12st using my own plan. But when I put most of it back on again I was ready to give up.

Then a chance comment from a colleague stopped me in my tracks. "Karen," she said, "you'd be really pretty if you just lost some weight."

It was an off-the-cuff remark but I was deeply embarrassed and upset. Still, I'm glad she said it because it gave me the push I desperately needed. I spoke to my doctor, who suggested a gastric band, but the idea of surgery horrified me so I decided to give dieting one last go.

I'd heard about Weight Watchers through friends but never tried it. In January 2012 I walked through the doors of my local group.

I'd heard horror stories about weight loss groups where your weight is shouted out to the whole group to shame you to slim but thankfully it was nothing like that.

I weighed in at 27st but my group leader Becky Vacher was supportive and discreet.

Following the plan brought much-needed control into my life. I got into a routine and mapped out what I was going to eat each day. I was regimented and focused so I didn't fall back into my bad old habits.

I was surprised to find that I could still eat most of my favourite foods, just in much smaller portions. However, my beloved takeaways had to go. I also made smart switches, such as swapping sugary cereal for porridge at breakfast and using extra lean mince for dinner.

As well as cutting down my portions I began to weigh out all of my ingredients.

While I used to have a whole pint of milk on a huge bowl of cereal for breakfast, I limited myself to two Weetabix and a splash of skimmed milk.

I lost 10lb in my first week and the whole group cheered, which gave me a real boost.

I also joined a gym. When I first started I could barely move but soon I could keep going on the treadmill for half an hour. These changes had a massive impact and in a year I lost 7st 2lb.

I have since gone on to shed a total of 11st 7lb, taking my weight down to 15st 7lb. I now weigh less than when I left school.

I also find it's the little things in life that make me the happiest.

A few weeks ago I put on a size 16 skirt for the first time and felt so proud of myself. My seatbelt now fits around me and when my husband Greg, an engineer, hugs me his arms go all the way around.

He loves my new figure and has lost six stone himself because my diet means he eats so much more healthily now too.

I've had my wedding and engagement rings reduced by seven sizes and I no longer have to hide in black clothes.

I have more energy and enthusiasm and there have been other benefits too: I even got promoted at work because of my new confidence, which is amazing. This summer is going to be a real first for me because I have booked a flight to Copenhagen to watch my brother Chris in an Ironman competition.

I've never been abroad before because I wouldn't have fitted in the plane seat. Keeping the weight off is an ongoing battle and I have bad days as well as good but I've learned that it's getting back on track that's important.

I'm turning 40 in September and would really love to be at my target of below 11st by then. I have no idea what the future holds but I'm sure it's going to be filled with experiences I'd never thought possible.